linux-kernel - Re: tpm_tis_spi takes minutes to probe

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Date: Fri, 17 May 2024 18:42:04 +0300
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Vitor Soares" <ivitro@...il.com>, <linux-integrity@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Cc: <jgg@...pe.ca>, <peterhuewe@....de>, <vitor.soares@...adex.com>
Subject: Re: tpm_tis_spi takes minutes to probe

On Fri May 17, 2024 at 5:53 PM EEST, Vitor Soares wrote:
> Greetings,
>
> I'm using the tpm_tis_spi.ko module and it is taking several minutes to probe on
> kernel:
>  - commit ea5f6ad9ad96 ("Merge tag 'platform-drivers-x86-v6.10-1' of
> git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86")
>
> root@...din-imx8mm-07317726:~# time modprobe tpm_tis_spi 
> [   57.534597] SPI driver tpm_tis_spi has no spi_device_id for atmel,attpm20p

This was added in 6.9:

$ git --no-pager log -1 3c45308c44eda
commit 3c45308c44eda6cc3343a48341a82b96753c8a13
Author: Lukas Wunner <lukas@...ner.de>
Date:   Sat Jan 13 18:10:52 2024 +0100

    tpm_tis_spi: Add compatible string atmel,attpm20p
    
    Commit 4f2a348aa365 ("arm64: dts: imx8mm-venice-gw73xx: add TPM device")
    added a devicetree node for the Trusted Platform Module on certain
    Gateworks boards.
    
    The commit only used the generic "tcg,tpm_tis-spi" compatible string,
    but public documentation shows that the chip is an ATTPM20P from Atmel
    (nowadays Microchip):
    https://trac.gateworks.com/wiki/tpm
    
    Add the chip to the supported compatible strings of the TPM TIS SPI
    driver.
    
    For reference, a datasheet is available at:
    https://ww1.microchip.com/downloads/en/DeviceDoc/ATTPM20P-Trusted-Platform-Module-TPM-2.0-SPI-Interface-Summary-Data-Sheet-DS40002082A.pdf
    
    Signed-off-by: Lukas Wunner <lukas@...ner.de>
    Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@...nel.org>
    Cc: Tim Harvey <tharvey@...eworks.com>
    Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>

linux-tpmdd on  tpm2_key 
$ git describe --contains 3c45308c44eda
tpmdd-v6.9-rc1~2

> [   57.560684] tpm_tis_spi spi2.1: 2.0 TPM (device-id 0x3205, rev-id 1)
> [   57.584943] tpm tpm0: A TPM error (256) occurred attempting the self test

Course of event is I think:

	rc = tpm2_do_selftest(chip);
	if (rc && rc != TPM2_RC_INITIALIZE)
		goto out;

	/* 1. TPM_RC_INITIALIZE */
	if (rc == TPM2_RC_INITIALIZE) {
		/* 2. Branches here. */
		rc = tpm2_startup(chip);
		if (rc)
			goto out;

		rc = tpm2_do_selftest(chip);
		if (rc)
			goto out;
	}

	/* 4. Second self-test successful. */

It is possible that there is a performance regression given multitude
of HMAC changes. It would likely had to be in tpm2_do_selftest(), since
it is the most time-consuming function.

I checked the timeouts etc. but in the first seek did find anything
obvious.

BR, Jarkko